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Old 10-25-2016, 10:55 PM
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Hei cap and rotor melted?

I was driving on the highway doing about 75mph and hit a bump. The engine cut out as soon as I hit the bumb and never turned back on . I got it home to find the rotor totally melted. It looks like a bomb went off in the center of the rotor. Any ideas on what caused this. Dist is less than 5 years old , bought new. cap and rotor is about 1-2 years old. I do have a external coil on the HEI with the MSD cover to connect the external coil.

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Old 10-25-2016, 10:57 PM
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in cap... center button under coil first.. then silicone disc.. folded ground strap... coil... 4 screws... looking at blank areas inside cap to verify the screws are not protruding thru where they will steal the spark right off the rotor and make the weirdest misfire you have ever seen.




edit. i have not seen how the external coil connection aligns..

coil
ground strap
silicone disc
carbon contact
cap.
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Old 10-25-2016, 11:08 PM
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Old 10-25-2016, 11:09 PM
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Old 10-25-2016, 11:37 PM
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that is the most impressive rotor failure i have ever seen in 36 years under the hood..

what does the inside of the cap look like... and when you disassemble the cap components..

that is worth posting over at

https://www.reddit.com/r/Justrolledintotheshop/new/


r/Justrolledintotheshop on Imgur


the MSD external coil adapter kit comes up as a mallory image... http://documents.msdperformance.com/29049.pdf

this seems to be the msd version.. https://static.summitracing.com/glob...1_frm28677.pdf

Last edited by 69612; 10-25-2016 at 11:42 PM.
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Old 10-26-2016, 11:13 AM
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The caps carbon center button wore through the tab, resulting arcing burned everything in the vicinity.

How many miles since it was changed, age has little to do with it.
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Old 10-26-2016, 01:25 PM
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Thanks for the help guys. I found the culprit to be one of the rotor screws backed out. I guess when I hit the bump it popped the rotor up. I was not able to look at it last night. I just had a chance to open the dist up and noticed the screw to hold down the rotor was missing. I guess the screw popped out and thats was all she wrote. I replaced the rotor and cap and the engine is running
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Old 10-26-2016, 02:01 PM
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That's a pretty messy mess! Not seen one like that ever..

Yeah, the center button wore out and got tangled up in the top of the rotor. I've had a lot of the spark tracking but not that bad. I would guess the cap is mangled too. You can see where the end of the rotor hit the terminals. The missing screw probably started the whole thing.

Even with the MSD problems they can throw a heathy spark a long ways when they work.

My cap and rotor only last about 6000 miles. The button gets worn then the rotor contact starts doing damage all over. The new caps come with a breather hole but I don't know if it helps or not.
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Old 10-26-2016, 02:49 PM
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I had a similar experience like you but it did not look as bad but I installed a new cap and rotor during the summer of 2014 and I don't drive too much but last year while I was out of town and driving by a Walmart I noticed my truck started to misfire and all of a sudden just quit. I had basic tools on me but nothing for a distributor wrench wise. I had to get a ride home and I came back the next day and I had a hole that was melted through my cap and upon taking the parts out I noticed my carbon spring or whatever its called was not sticking through the cap like I am used to it and it turns out I put the rubber piece in first and then the carbon button along with the ground strap and coil how they are supposed to go. With the carbon button sticking up so high from the rotor it made a lot of resistance and heat and burnt through. After I was done it fired right up and has worked like a charm since then. A lesson for me lol. Hope you get it figured out. I must say I have never seen a meltdown like that.
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Old 11-01-2016, 06:44 AM
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Quote:
Originally Posted by Big Truck Driver View Post
Thanks for the help guys. I found the culprit to be one of the rotor screws backed out. I guess when I hit the bump it popped the rotor up. I was not able to look at it last night. I just had a chance to open the dist up and noticed the screw to hold down the rotor was missing. I guess the screw popped out and thats was all she wrote. I replaced the rotor and cap and the engine is running
Almost looks like the missing screw got between the button and tab. A buddy had the same thing happen to his MSD rotor but when the screw came out the rotor twisted into the cap contacts and broke. No spectacular nuclear meltdown like yours...
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